1. Field of the Invention
The invention relates to turbojets and, more particularly, to an adjustment system for centering a turbojet wheel within the stator ring that encircles it wherein the invention is particularly advantageous when said wheel forms part of the high pressure stage of a turbine in a turbojet engine, a stage in which the narrow centering tolerances of the wheel are particularly critical and wherein the invention also concerns a turbojet equipped with means enabling said adjustment system to be applied.
2. Description of the Prior Art
The most common known solution for performing the above centering operation consists of the following steps: creating a finishing allowance when machining the inner cylindrical bearing of the turbine frame, the inside of which will be housed a fixed journal bearing supporting the shaft and lying closest to the wheel; dry-run mounting of at least that portion of the stator frame that includes the bearing and the ring; measuring the relative eccentricity of the bearing and ring; and finishing machining of the bearing so as to bring this eccentricity within tolerance limits.
This solution is reliable but has the disadvantage of requiring the dry-run mounting. This drawback is particularly inconvenient when the turbine is of modular design, i.e., when the HP (high pressure) stage is made completely independently of the MP (middle pressure) or LP (low pressure) stage to which it must be joined without alteration.
In French Pat. No. 2,434,269 it has already been proposed that annular bearings set off-center with respect to the axis of the jet be provided on the intermediate rings that join the portion of the turbine frame that includes the stator ring to the portion that includes the fixed bearing support. The shaft is therefore centered at the time the two portions of frame are assembled by giving these intermediate rings set orientations calculated from the results of measurements of the relative eccentricity of the stator ring and the bearing surface. This solution makes it necessary to make these intemediate ring bearings with different degrees of off-centering in order to obtain compensation for the off-centering of the shaft through vector addition of the off-centering of the intermediate rings. The solution becomes practically inapplicable when the diameters of the rings are large.